How can I get over anxiety attacks so I can give a presentation next week?

I have severe anxiety and I've been having anxiety attacks for months. I can't take prescription pills because I'm an air traffic controller and I've been trying herbs (valerian, ignatia, pion flower) but nothing seems to work. And I ALWAYS have anxiety attacks when I have to speak to a group and next week and have to give a short presentation to everyone in my work and I'm petrified of having an anxiety attack. Please help me.